Lubricating composition

ABSTRACT

A MINERAL LUBRICATING OIL, PARTICULARLY A HYDROGENATED MINERAL LUBRICATING OIL IS STABILIZED AGAINST PHOTO-DETERIORATION BY INCORPORATING THEREIN A SMALL AMOUNT SUFFICIENT TO INHIBIT SUCH DETERORATION OF EACH OF (1) AN ORTHOHYDROXYBENZOPHENONE, E.G., 2,2&#39;&#39;-DIHYDROXY-4-METHOXYBENZOPHENONE AND (2) AN ALIPHATIC PRIMARY AMINE, E.G., A C8-C18 ALKYL AMINE OR MIXTURE OF C8-C18 ALKYL AMINES.

United States Patent 3,702,299 LUBRICATING COMPOSITION Robert J. Hartle, Gibsonia, and Joseph J. McGrath,

Monroeville, Pa., assignors to Gulf Research & Development Company, Pittsburgh, Pa. No Drawing. Filed Nov. 13, 1970, Ser. No. 89,506 Int. Cl. Cm 1/20, N32 US. Cl. 25251.5 R 4 Claims ABSTRACT OF THE DISCLOSURE A mineral lubricating oil, particularly a hydrogenated mineral lubricating oil is stabilized against photo-deterioration by incorporating therein a small amount sufiicient to inhibit such deteroration of each of (1) an orthohydroxybenzophenone, e.g., 2,2'-dihydroxy 4 methoxybenzophenone and (2) an aliphatic primary amine, e.g., a C -C alkyl amine or mixture of Cg-Cm alkyl amines.

This invention relates to an improved lubricating composition and more particularly to a mineral lubricating oil composition having improved resistance to deterioration when exposed to actinic radiation and in particular when exposed to ultraviolet light characteristic of normal sunlight.

The trend in designing more efficient and more economical automotive and aircraft engines has accentuated the need for lubricants which will eifecti'vely lubricate bearings operating under severe conditions over extended periods of time. The lubricant in addition to its normal lubricating characteristics must also be one which is highly resistant to oxidative deterioration when exposed to actinic radiation. Products 'which are formed upon oxidation of the oil are acidic in nature and thus exert a corrosive effect on metal surfaces with which the oil comes in contact. Oxidation of the oil, particularly oxidation initiated by exposure to ultraviolet light is further undesirable in that the oil discolors and becomes hazy in appearance.

For many years, highly refined parafi inic oils have been used as base oils in forming lubricating compositions. By the term highly refined parafiinic oils we mean a petroleum lubricating oil which has been refined by one of the more drastic refining methods known in the art, for example, by conventional solvent extraction and aluminum chloride refining adapted to remove all or substantially all of the unsaturated and aromatic constituents of the oil. Aluminum chloride refined or solvent extracted parafiinic oils, such as Pennsylvania oils, have provided excellent base oils for many lubricating compositions. Likewise, drastically refined Mid-Continent and Gulf Coastal oils have been widely used as base oils in forming lubricants.

In addition to these refining methods, lubricating oils of high quality have been obtained by hydrogenating various charge stocks derived from Pennsylvania, Mid- Continent, West Coast, Middle-East crudes, etc. It has been known, for example, that improved lubricating properties can be obtained when the lubricating oil stocks are 3,702,299 Patented Nov. 7, 1972 ice treated with hydrogen. Treating some lubricating oil stocks with hydrogen, for example, has resulted in obtaining stocks for making excellent multigrade lubricants, i.e., lubricants suitable for use under a wide range of temperatures. Regardles of the treatment to which the various charge stocks are subjected, the mineral lubricating oil per se, which is obtained is not completely satisfactory for use under the severe conditions encountered in some of the current engines. Not all of the hydrogenated oils, for example, are resistant to deterioration when exposed to ultraviolet light. There is some evidence that naturally occurring oxidation inhibitors in distillate oils are destroyed during some hydrogenation processes and that materials are formed during some hydrogenations which give rise to photodegradation of the oil upon exposure to ultraviolet light.

We have discovered that a mineral lubricating oil normally tending to discolor and to become hazy upon exposure to ultraviolet light can be efiectively inhibited against such undesirable changes by incorporating ina major amount of the mineral lubricating oil a small amount of each of (1) an orthohydroxybenzophenone having the following structural formula:

OH X QM? Z Y wherein X, Y and Z each represents a member selected from the group consisting of hydrogen, alkyl, alkoxy and hydroxy radicals and wherein each of said alkyl and alkoxy radicals contains from 1 to 18 carbon atoms and (2) an aliphatic primary amine having the following formula:

RNH

wherein R is selected from the group consisting of alkyl radicals containing from 8 to 18 carbon atoms, octadecenyl and octadecadienyl radicals. The alkyl radical can be either straightor branched-chain. Thus, the lubricating oil composition of our invention comprises a major amount of a mineral lubricating oil normally tending to discolor and to form a haze upon exposure to ultraviolet light and a small amount, sufiicient to substantially inhibit such discoloration and haze formation, of each of (1) an ortho-hydroxybenzophenone having the structural formula shown hereinabove and (2) an aliphatic primary amine having the formula shown hereinabove. Certain combinations of (1) and (2) also provide a synergistic improvement in stability against discoloration and haze formation.

The ortho-hydroxybenzophenone and the primary amine are each employed in amounts of about 0.001 to about 0.1 percent by weight based on the Weight of the total lubricating composition. Synergistic improvement is noted when both of these materials are present in the lubricating oil, particularly hydrogenated mineral lubricating oils in amounts of about 0.002 to about 0.05 percent by weight of the total lubricating composition. In any event, each material is added to the oil normally tending to discolor and to form a haze upon exposure to ultraviolet light in a small amount sufiicient to substantially inhibit such discoloration and haze formation.

The X, Y and Z radicals in the ortho-hydroxybenzophenone can be either like or unlike substituents including hydrogen, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, hexadecyl, octadecyl, methoxy, ethoxy, propoxy, butoxy, pentoxy, octoxy, decoxy, octadecoxy and hydroxy radicals. We prefer dihydroxybenzophenones containing at least one lower, i.e., C to C alkyl or alkoxy radicals.

The ortho hydroxybenzophenones and the aliphatic primary amines employed according to the invention are available commercially and/or can be prepared by known chemical procedures. Neither the compounds per se nor their method of preparation constitute any portion of the invention.

Specific examples of the ortho-hydroxybenzophenones which fall within the scope of the structural formula shown hereinabove include:

2-hydroxybenzophenone 2-hydroxy-4-methylbenzophenone 2-hydroxy-4-ethylbenzophenone 2-hydroxy-4-n-propylbenzophenone 2-hydroxy-4-n-butylbenzophenone 2-hydroxy-4-n-octylbenzophenone Z-hydroxy-4-n octadecylbenzophenone 2-hydroxy-5-methylbenzophenone 2-hydroxy-4'-methylbenzophenone 2-hydroxy-3',5 ,5 -trimethylbenzophenone Z-hydroxy-4-methoxybenzophenone 2-hydroxy-4-ethoxybenzophenone 2-hydroxy-4-propoxybenzophenone Z-hydroxy-4-butoxybenzophenone Z-hydroxy-4-methoxy-4'-methylbenzophenone 2-hydroxy-4-methoxy-4-ethylbenzophenone 2-hydroxy-4 methoxy-4'-propylbenzophenone 2-hydroxy-4-methoxy-4'-n-butylbenzophenone 2-hydroxy-4-methoxy-4'-tert-butylbenzophenone 2-hydroxy-4-ethoxy-4'-methylbenzophenone 2-hydroxy-4-ethoxy-4'-ethylbenzophenone 2-hydroxy-4-ethoxy-4-propylbenzophenone 2-hydroxy-4-ethoxy-4'-butylbenzophenone 2hydroxy-4,4'-diethoxybenzophenone 2-hydroxy-4-ethoxy-4'-methoxybenzophenone 2-hydroxy-4-ethoxy-4'-propoxybenzophenone 2-hydroxy-4-ethoxy-4'-butoxybenzophenone 2-hydroxy-4,4-dimethoxybenzophenone 2-hydroxy-4,4'-dimethoxy-2-methylbenzophenone 2-hydr0xy-4,4-dimethoxy-Z-ethylbenzophenone 2-hydroxy-4-propoxy-4' methoxybenzophenone 2-hydroxy-4,4',5'-trimethoxybenzophenone 2-hydroxy-4,4', -tributoxybenzophenone 2-hydroxy-4-ethoxy-2',4'-dibutylbenzophenone 2-hydroxy-4-butoxy-4,5'-dimethoxybenzophenone 2,2'-dihydroxybenzophenone 2,2'-dihydroxy-3-methylbenzophenone 2,2-dihydroxy-4-methylbenzophenone 2,2.-dihydroxy-S-methylbenzophenone 2,2-dihydroxy-5-ethylbenzophenone 2,2-dihydroxy-5-n-propylbenzophenone 2,2-dihydroxy-S-n-butylbenzophenone 2,2'-dihydroxy-5-n-octylbenzophenone 2,2'-dihydroxy-5-n-octadecylbenzophenone 2,2-dihydroxy-3-rnethoxybenzophenone 2,2'-dihydroxy-4-methoxybenzophenone 2,2-dihydroxy-S-methoxybenzophenone 2,2'-dihydroxy-6-methoxybenzophenone 2,2-dihydroxy-4,4-dimethoxybenzophenone 2,2-dihydroxy-4,4-diethoxybenzophenone 2,2'-dihydroxy-4,4'-dipropoxybenzophenone 2,2'-dihydroxy-4-methoxy-4'-ethoxybenzophenone 2,2'-dihydroxy-4-methoxy-4'-propoxybenzophenone 2,2-dihydroxy-4-methoxy-4'-butoxybenzophenone 4 2,2-dihydroxy-4-ethoxy-4'-butoxybenzophenone 2,3-dihydroxybenzophenone 2,4-dihydroxybenzophenone 2,3 -dihydroxy-4,4'-dimethoxybenzophenone 2,2,3-trihydroxybenzophenone 2,2,4-trihydroxybenzophenone 2,4,4'-trihydroxybenzophenone 2,2',3 -trihydroxy-4'-methoxybenzophenone 2,2,4,4'-tetrahydroxybenzophenone Specific examples of the aliphatic primary amines which fall within the scope of the formula shown hereinabove include:

n-octylamine tert-octylarnine n-decylamine n-dodecylamine tert-dodecylamine n-tetradecylamine n-hexadecylamine n-octadecylamine tert-octadecylamine n-octadecenylamine n-octadecadienylamine A preferred group of the aliphatic primary amines includes the so-called fatty amines. The fatty amines are those derived from fatty acids by conversion of the acids to nitriles, followed by catalytic hydrogenation of the nitriles to amines. While we can use a single amine, we can also use a mixture of amines such as the amines obtained upon conversion of coconut oil fatty acids into the corresponding amines. The mixture of amines obtained from coconut oil fatty acids contains a major amount of ndodecylamine with minor amounts of n-octyl, n-decyl, n-tetradeclyl, n-hexadecyl, n-octadecyl, n-octadecenyl and n-octadecadienyl amines. Commercially available mixtures of the fatty amines are the Armeens marketed by Armour and Company. Armeen C and Armeen CD" are mixtures of C to C aliphatic primary amines. A more specific description of the composition of Armeen C and Armeen CD is found in Table I.

TABLE I Armeen Armeen Make-up, percent by Weight:

n-Octyla n-Decylamine n-Dodecylamine... n-Tetradecylaminen-Hexadecylamine 8 8 n-Octadecylamine 5 5 n-Octadecenylamine 5 5 Characteristics:

Mean molecular weight of primary amine content: M01 combining Weight Percent primary amine by titration Approximate melting point, C

TABLE H Primene 81-R Formula:

'cu za z t-C13H 7NHg Mol weight 17 1-218 Average mol weight 191 Boiling range at 760 mm Specificgravity, 25 C. 0.813 Refractive index, 25 C. 1.423 Flash point (Tag, O.C.) F" 205 Further data on Primene 81-R are found in the booklet entitled, Tertiary-Alkyl Primary Amines dated Oct. 1, 1956 and published by Rohm & Haas Company.

The ortho-hydroxybenzophenone and the aliphatic primary amine can be incorporated in the lubricating oil in any sequence. The materials can be added as such or in the form of a concentrated oil solution thereof. The use of a concentrate is particularly advantageous to facilitate the blending operation.

- The mineral lubricating oil to which the orthohydroxybenzophenone and the aliphatic primary amine are added can be any oil having a viscosity within the range of common lubricating oils. The mineral oil, for example,

ing oils for a specific purpose such as an oiliness and extreme pressure agent, antioxidant, a corrosion inhibitor, a foam suppressant, a dye, a viscosity index improver, and the like. These agents can be separately added to the oil or they can be added in the form of an oil solution thereof which contains one or more of such additives. If desired, the solution can also contain the orthohydroxybenzophenone and the aliphatic primary amine.

In order to illustrate the reduced discoloring and reduced haze formation of lubricating compositions of the invention, a hydrofinished oil is compared with the same oil containing an ortho-hydroxybenzophenone and an aliphatic primary amine separately and combinations thereof. The test employed in evaluating the lubricating compositions is an accelerated test used to predict the probable eifect of solar radiation on lubricating oil compositions. The accelerated test comprises exposing the compositions to ultraviolet radiation and noting the time required to form haze and to form a color of 1.5 as determined by ASTM D1500. The source of ultraviolet radiation is a 450 watt Hanovia high pressure mercury arc lamp at a distance of 7 inches from the sample. The results of these tests are summarized in Table III. The mineral lubricating oil employed in the experimental work reported hereinafter is a hydrofinished oil having as typical characteristics an API gravity of 32.4; a viscosity of 106 SUS and 40 SUS at 100 and2l0 B, respectively; a viscosity index of 100; a flash point of 385 F.; a fire point of 445 F., a pour point of ,l-l-S" F. and a color can be either a refined or semi-refined paraflinic, naph- ASTM D1500 of 0.5.

' TABLE m A B C D E F Mineral lubricating oil 100 100 100 100 100 100 Added, percent by Weight:

2,2'-dihydroxy-4-methoxybenzophenone 0.01 0.03 0. 01 "Armeen C" e 0. 02 0.03 0.02 UV lamp stability, irradiation time in hours 1:

Color of 1.5 15 15 14 30 32 35 Haze a See Table I ior description of Armeen C."

b 011 samples in hall-filled 4oz. bottles exposed to a 450 watt Hanovia mercury arc lamp at a distance of 7 inches.

ASTM D1500 color determined periodically. Color plotted against time and the curve interpolated to give hours at a color oi 1.5.

thenic or asphalt base oil. A mineral oil which has been treated with hydrogen .and which is subject to photodegradation caused by ultraviolet light is particularly suitable as a lubricating oil base for preparing a lubricating oil composition of the invention. For this reason, a preferred embodiment of the invention utilizes a mineral oil which has been treated with hydrogen whereby extensive hydrogenation of the olefinic and/ or aromatic constituents present in the charge stock has been effected. The hydrogen treating process may be either a hydrofinishing prr cess or a hydrotreating process. The method by which a hydrogenated mineral lubricating oil is obtained is not a part of the present invention. The mineral oil content of the composition of the invention will vary depending upon the ultimate use for which the composition is intended. In general, however, the mineral oil content comprises at least 99 percent by weight of the total composition. The particular mineral lubricating oil as well as the exact amount of such oil employed, therefore, depends upon the characteristics desired in the final composition.

The lubricating oil composition of the invention can contain other addition agents normally added to lubricat- 5 D1500 color of 1.5 in 15 hours. When 0.02 and 0.03

percent by weight of Armeen C" are added to the oil, there is no improvement in discoloration although there is considerable improvement in haze formation. When 0.01 and 0.03 percent by weight of 2,2'-dihydroxy-4-methoxybenzophenone are addeed to the oil there is some improvement in the color stability and also some improvement in haze formation at the 0.03 percent concentration. When 0.01 percent by weight of 2,2'-dihydroxy-4-methoxybenzophenone is added in conjunction with 0.02 percent by weight of Armeen C, the improvement obtained with respect to discoloration and haze formation is greater than would be expected from an observation of the oil containing each of the materials separately.

In another series of experiments utilizing smaller amounts of Armeen CD instead of Armeen C, the results obtained are similar to those noted above, except to a lesser degree. The results obtained with Armeen CD and 2,2 dihydroxy 4 methoxybenzophenone are summarized in Table IV.

Color of 1.5 Haze I See Table I for description oi Armeen CD." Oil samples in hali-fil1ed 4-oz. bottles exposed to a 450 watt Hanovia mercury arc lamp at a distance of 7 inches.

B ASTM D1500 color determined periodically. Color plotted against time and the curve interpolated to give hours at a color of 1.5.

The above data in Table IV again illustrate synergism hibit such discoloration and haze formation, of each of with respect to the combination of Armeen CD and (1) 2,2'-dihydroxy-4-methoxybenzophenone and (2) a 2,2'-dihydroxy-4-methoxybenzophenone. In this particular mixture of C to C aliphatic amines.

series of experiments synergism is not as pronounced due 3. The lubricating composition of claim 2 wherein the to th lower concentration of additiv 5 2,2-d1hydroxy-4-methoxybenzophenone and the mixture Specific examples of other compositions within the of C to C aliphatic amines are each present in amounts scope of the invention are set forth in Table V.

TABLE v Make-up, percent by weight Composition M N o P Q, R s '1 U v w Mineral lubricating oil 99. 999 99. 945 99. 98 99. 945 99. 899 99.9 99.99 99. 998 99.8 99. 9s 99. 934. o-Hydroxybenzophenoue:

2-hydroxy+methoxybenzophenone 0. 001

z nydroxy-4-methoxy-4'-t-butylbenzophenone 0.005 0. 1

2-hydroxy-4-ethoxy-4'-propoxybenzophenone 0. 01

2-hydroxy-4,4, 6-trlbutoxyb enzopbenone 2,2-dihydroxy-5-ethylb enzophenone 2,2-d.ihydroxy4,4-dimethoxybenzophenone 2,3-dihydroxybenzophenone I 2,2,3-trihydroxy-4"methoxybenzophenone Primary amine:

n-Octylm'nlna t-Octylamine n-Dodecylaminet-Dodecylamine n-Oetadecy t-Oetedecylamlue.

"Armeen C n".-. .i. "Prlmene 81-R" b 0, 001

I See Table I for description 01 "Armeen C." 9 See Table II (or description oiPrin1ene 81-R."

While our invention has been described with reference of about 0.002 to about 0.05 percent by weight of the to various specific examples and embodiments, it will be composition.

understood that the invention is not limited to such ex- 4. The lubricating composition of claim. 2 wherein the amples and embodiments and may be variously practiced e al ubricating Oil is a hydmgeflated e al lubriwithin the scope of the claims hereinafter made. eating oil.

We claim: References Cited 1. A lubricating composition comprising a major UNITED STATES PATENTS amount of a mineral lubricating oil normally tending to discolor and to form haze upon exposure to ultraviolet f et 22: light and a small amount, suflicient to substantially inhibit 1888023 11/1932 323: "5 such discoloration and haze formation, of each of (1) a 2,370,552 2/1945 Lincoln et aL 1 252 5l s R dihydroxybenzophenone containing only an alkoxy radical which contains from 1 to 4 carbon atoms and (2) a mix- DANIEL E. WYMAN Primary Examiner ture of C to C aliphatic primary amines.

2. A lubricating composition comprising a major SHINE Asslstant Exammer amount of a mineral lubricating oil normally tending to U S cl XR discolor and to form haze upon exposure to ultraviolet light and a small amount, suflicient to substantially in- 52 R, 407 

